1. Field of the Invention
The present invention relates to heat-sensitive recording materials and a recording process for using the same. In more detail, the present invention relates to heat-sensitive recording materials using a soluble material which becomes insoluble by application of heat energy and a process for using the same.
2. Description of the Prior Art
Hitherto, various heat-sensitive recording materials and processes for using the same are known. For example, Japanese Patent Publication No. 9718/69 discloses that images are obtained by increasing the degree of swelling or the dissolution rate in water of portions of a heat-sensitive recording layer, composed of gelatin as a main ingredient, to which heat has been applied. Japanese Patent Publication No. 27919/71 discloses heat-sensitive recording materials comprising a heat-sensitive recording layer composed of a certain type of natural high molecular weight compound or synthetic high molecular weight compound, which are processed with a liquid capable of selectively removing portions of the recording layer which have been heated. The above described heat-sensitive recording layers are all characterized by that the degree of swelling and the dissolution rate increase in portions where heat was applied.
On the other hand, Japanese Patent Publication No. 9716/69 discloses recording materials comprising a heat-sensitive recording layer composed of polyvinyl alcohol having 95% or more vinyl alcohol units as a main ingredient, in which the water permeability, swelling property or dissolution rate of the recording layer is reduced by application of heat to the recording layer.
However, in these materials it is difficult to reduce the water permeability, the swelling property or the dissolution rate of the recording layer to the degree necessary to form practical images by application of heat. Admixing finely divided thermoplastic hydrophobic materials such as polyethylene, etc., to the heat-sensitive layer has been proposed to improve the above described defect.